My major gripe with the PS3 (and its predecessors for that matter) is the controller. I hate the shape and feel of it. By contrast, the 360 controller feels fantastic and far more comfortable to me, but sadly the console it comes with has a habit of dying for no apparent reason. Game-wise, I've never really liked any of the Sony-exclusive titles and have preferred the Xbox titles but in this age of money grubbing, almost everything comes out on everything at some point.
Including GTA. GTA 5 won't be Sony exclusive. It might start that way, but it'll be ported, same as GTA 3 and its spinoffs were.
Meh, I think if you're asking on here, you've probably already decided to buy one, but still want us to convince you that you've made the right decision. In which case, just do it. There really isn't one "right" console this generation anyhow. They're all about equal.